The Resonant Remains of Broken Chains from Major and Minor Mergers

• DOI: 10.48550/arxiv.2408.10206
• Publication Date: 2024-08-19
• Authors: LI Ri-xin; Eugene Chiang; Nick Choksi; Fei Dai
• Keywords: Minor (academic)

Observations with the Transiting Exoplanet Survey Satellite and Kepler have revealed that practically all close-in sub-Neptunes form in mean-motion resonant chains, most of which unravel on timescales 100 Myr. Using a series N-body integrations, we study how planetary collisions resulting from destabilization chains produce distribution orbital periods observed among mature systems, focusing fine structures remain post-instability. In their natal planets near first-order resonances period ratios just wide perfect commensurability, driven there by disk migration eccentricity damping. Sufficiently large libration amplitudes (of unknown origin) are needed to trigger instability. Ensuing between ("major mergers") erode but do not completely eliminate pairs; survivors avoid mergers show up as narrow "peaks" commensurability histogram neighboring-planet ratios. Merger products exhibit broad range ratios, each peak spawning continuum given resonance. These continua may fill relatively closely separated such 5:4, 4:3, 3:2, fail bridge gap 3:2 2:1. Thus "trough" manifests short 2:1 resonance (and only resonance), observed. Major perfect, generate collisional debris undergoes "minor mergers" planets, many cases further widening pairs. With this dynamical activity, free eccentricities pairs, extension phases transit timing variations (TTVs), readily excited. Because non-resonant merger products, they predicted higher masses than planets.